The present invention relates to a random access to a recording memory of spoken words through scanning of an electron beam controlled by a digitally addressible control which is particularly useful to construct sentences by assembling different length words one after another taken at random from the memory. The invention also applies to a recorded memory of identifiable audio sounds and electrical impulses.
The problem of man-machine interfacing is becoming acute with the increase utilization of digital computers. Many attempts in the past were directed to facilitate rapid communication exchange between man and computer which have been implemented by approaches such as light pen inputting, computer movies, high speed print out, teletype consoles, etc. In regard to the field of transportation, for example, using hardware such as airplanes, space vehicles and numerous other means of transportation, computer aided direction and control are necessary. There has been developed a variety of specific gauges to guide the pilot. Most of these indicators are visual and therefore tax the concentration of the pilot or human being in command or in charge of the control.
The audio channeling of information directly from a computer to a man's ears is presently, at best, rudimentary, typically confined to audio warning buzzes and/or very simple prerecorded messages. In contrast to this, sophisticated audio messages of the type "pressure dropping rapidly in rear rudder control system, suggest immediate lowering of base system hydraulic pressure to 16 psi; begin reflushing procedure 938, repeat 938" are presently unheard of forms of audio messages. Some of the underlying problems concerning the failure by the art to provide such sophisticated audio messages have resulted from factors such as random access to word memories are presently constrained by cost and size to encompass vocabularies of 50 to 100 words which is totally inadequate for composition of meaningful sentences that might cover the multiplicity of situations and occurrences, for example, during an airplane flight. Most current methods of random accessing spoken words using rotating discs or belts of magnetic material require multiple magnetic heads or some other type of mechanical system for rapid access. Such rapid access mechanical systems are expensive, bulky and generally require very critical adjustment. Systems of these types, except for the most costly and sophisticated, are based on a fixed word length access. In other words, the time between the beginning of successive words is selected to accommodate the longest word in the vocabulary. Thus, a rotating belt-type of magnetic recording system or disc-type would have a preselected speed such that the longest word of the vocabulary is written around one full rotation of the belt or disc. This has the marked disadvantage that when short and long words are included in the vocabulary it is necessary to wait for a complete revolution of the recorder for short words. As a result, there is produced unnatural breaks in the speech that lead to a loss in intelligibility. Most current systems ae restricted to one prime inflection per word which is generally produced by the system in a monotone. Thus, information conveyed normally in the inflection of words during normal conversation is entirely missing. The choice of multiple head tape or disc-type recorders with all their weight and mechanical complexity and generally high cost are considered to be an unacceptable medium due to the limited number of words in the vocabulary which they replay at a fixed recording interval without meaningful word inflections.
One of the primary problems that must be dealt with to construct a machine which will form sentences by butting together words pulled from a random memory may be understood when one considers that spoken words take between 0.25 to 2 seconds to enunciate. However, in most languages the time between the ending of the word and the beginning of the enunciation of the next word may be as short as 10 to 50 milliseconds. Thus, random access to a memory containing a word vocabulary should be completed within 10 to 50 milliseconds and then playback of the word during a one second time duration. This rapid access time followed by the slow rate for replay places requirements that exist no matter what form the system may take, whether magnetic discs, magnetic core memory, etc. in order that information storage capacity is not wasted during the slow rate for the audio signal replay.
Since practically all of the present systems require movement such as rotation of a disc or belt, it is extremely difficult and expensive in terms of the required hardware to obtain the desired position of the tape relative to the playback head in 10 milliseconds following which the recording equipment must almost instanteously revert to a much slower read speed to replay the word. It is apparent that to maintain a constant high access speed, such as a disc memory does in a digital computer, wastes memory capacity during the slow bit per second voice enunciation. This rapid change between information play and information search is a considerable detriment to any high mass mechanical system intended as a spoken word memory. Other alternative systems ae known to include putting a multiplicity of playback heads over a magnetic recording so that at least one head is near to the desired word on the recording at any instant. This is impractical and expensive except for a limited vocabulary of fixed word length memories. So called buffered digital to voice converters are known wherein a sentence can be assembled at a video rate and then played back from a buffer store at an audio rate. Such converters, while useful, are also expensive and require a high speed mechanical drum or disc for word storage plus assembly circuitry for the sentence.